Abstract

This research explored effects of adding calcium oxide (CaO) and calcium peroxide (CaO2) in the rapid biological drying of dairy cattle manure. Using the static aerobic composting system, the composting experiment was carried out by means of natural ventilation combined with composting piles turned. In the presence of the CaO and CaO2, the temperature rose faster and reached the high temperature fermentation stage in advance 4-6 days during the compost. At the end of compost, the water content of CaO and CaO2 (cont.) group was decreased to 23.5% significantly. However, the diversity in four experiment group piles had little difference at the end of the compost, which only had some changes in the process of compost. In a word, it was CaO and CaO2 that would shorten the composting time, extend the high temperature stage, provide sufficient oxygen to meet the demand of the growth of aerobic microorganisms, had a good effect on dairy manure rapid drying and provided a new idea for dairy manure efficient treatment.

Keywords

Introduction

With the rapid development of livestock breeding industry
intensive and scale, livestock and poultry manure waste
increased dramatically, which has become the main source of
agricultural organic solid wastes in China [1]. According to the
statistics of the China Dairy Association, it was about 1.8 billion
fecal waste that was produced in China's dairy farming every
year, such as litter, feed residue and other waste [2]. A large
number of organic wastes piled up together could not be treated
properly, which posed a serious of threats to the surrounding
environment. Composting was an effective way to reduce
livestock manure and realized harmless treatment and resource
utilization [3-7]. According to the determination that moisture
content of non-water flushing livestock manure was about
65%~85% while the flushing livestock manure moisture content
could up to 90%. The high water content had a great influence
on the capacity, storage, transportation and processing effect [8-10]. How to effectively reduce the moisture content of livestock
and poultry feces was an important link in fecal treatment.

At present, there are many methods for livestock droppings
drying or reducing moisture in domestic and outside areas
[11,12]. In relative terms, the biological drying technology
attracted people's attentions because of low processing costs,
product safety and high efficiency. The term biological drying
of livestock manure was first proposed in 1984 by Jewell W
J who was an American scientist, Cornell University. The
principle was to use microbial decomposition of organic matter
produce energy and increase the emission of moisture in feces,
which was purposed to reduce water content then acknowledged
dryness in the process of composting. Jewell thought that microbial degradation effect was the most active when the
water content was 40% and the temperature was 60 degrees
centigrade using the principle of bio-drying and taking batch
compost, which based on the experimental research on mixing,
temperature, air velocity and other factors [13]. TL Richard
[14] thought composting, biological drying were related to
physical and biological processes. Arrhenius enzyme kinetics
equation and Albright stoichiometric equation were applied to
describe the relationship between factors about temperature,
ventilation rate and moisture emission rate. What’s more,
the corresponding model was built. It was inferred that every
kilogram of volatile solids could get rid of 1 kg water every
day. In other words, the moisture of manure could decrease
from 75% to 57% when consumed every kilogram volatile
solids every day. Richard et al [15] and Choi et al [16] put
forward the continuous batch or semi continuous composting
technology, which was based on the previous batch compost
on. The fully mixed aerobic biological reactor was designed
and manufactured as well. The experiment was done for 6 days
in the reactor. The result showed that the moisture of manure
could decrease by 0.46~0.78 kilogram when consumed every
kilogram volatile solids. Many experiments had shown that
moisture content was often higher than 30% after composting.
For example, Singh [17] took vegetable waste, sawdust and cow
dung as raw material for composting. The initial water content
was 63.5%~76%. After 20 days composting, the final moisture
content was 47.5%~72%; Roca-Perez et al [18] was in the test
of straw and sludge composting, the initial moisture content
was adjusted to 60.3%, after 90 days of composting, the final
moisture content was 39.9% ~42%.

Our country had done some research works in the disposal
of sludge drying and some organic waste using composting
technology [19,20]. Chang et al. [21] in Jiangsu Academy
of Agricultural Sciences conducted pig manure biological
drying test in Changshu city. The results showed that using the
batch compost, adding conditioner methods, the pig manure
moisture decreased from 700g/Kg to 550g/Kg during 20 days
composting. Chen [22] developed a complete set of equipment
for drying treatment on chicken manure fermentation. Using
this equipment, the moisture could be reduced from 650g/Kg
to 200g/Kg in 25~35 days biological fermentation. However,
there still had little research about alkaline treatment on
animal manure bio-drying researches in China. Some foreign
researchers had used calcium oxide as stabilizer. For examples,
Babyranidevi et al. [19] found that alkaline treatment on
municipal solid waste gave better composting performance.
Mijaylova et al. [23] researched alkaline stabilization with
lime produced a well stabilized and sterilized solution when
sludge was made for composting. Bulter et al. [24] used lime as
stabilizer for bio solids compost treatment to test three methods
for determining compost maturity. The study on CaO2 applied in
manure aerobic composting in China was studied by professor
Qu’s research group and they found that the addition of CaO2 in
cow manure was shortening the composting time, extended the
high temperature period and provided sufficient oxygen meeting
the growth needs of aerobic microorganisms [25].

In this experiment, cow dung and tobacco waste were used
as raw materials for fermentation. The CaO and CaO2 were
selected as stabilizer and oxygen supplement respectively. The
variation of temperature, moisture, pH, nitrogen, phosphorus,
potassium and the number of microorganism on cow manure
piles in each period were analyzed and compared in the process
of CaO, CaO2 and CaO combined with CaO2. It was expected
to know clearly the effect of CaO and CaO2 on fast bio-drying
technology during compost, which could provide theoretical
and technical guidance for the harmless treatment on cow dung
and compost production.

The research was a pilot scale experimental. The fresh cow dung
and tobacco were mixed in the ratio of 5:2 and then added CaO,
CaO2, CaO and CaO2, CaO and CaO2 (continuous addition) to
the mixture respectively. The mixture groups were piled into
the shapes of windrow with 3m long, 2m wide and 1.2m high.
The way for ventilation was through turning heap every 3 days during a period of 35 days. The specific experimental material
compositions were shown in Table 2.

Observing the physical characteristics of pile surface of
the reactor and determining the parameters of temperature,
moisture, organic matter, total nitrogen (TN), phosphorus
(TP) and potassium (TK) in the composting pile process. The
pile temperature was measured by ordinary thermometer with
minimum scale was 1℃. The water content was determined
according to the standard of NY525-2012 standard. The organic
matter content was measured by potassium dichromate capacity
method. Total nitrogen (TN) was measured by Kjeldahl method.
Total phosphorus (TP) was applied by spectrophotometry and
total potassium (TK) was applied by flame photometry method.
The relative species of cow manure piles in each period was
analyzed by 16S rRNA gene sequencing technology [26,27].

Results and Discussion

Changes and analysis of physical properties of compost
materials

Changes and analysis of compost materials: In the beginning,
the surface of group 2 pile was brown with a thick smell of
fresh cow dung while group 1, 3, 4 were dark brown and
fresh cow dung odor was significantly reduced because of
the addition of CaO. Then, the surface of group 1, 3, 4 piles
changed into black and produced white mycelium after 6 days
composting. The surface of group 2 pile also appeared white
mycelium but its surface color did not change. What’s more, the
agglomerate phenomena of group 1, 3 and 4 piles disappeared
after 15 days composting and these piles began to tend to be
uniform and loose. At the end of composting, the materials of
group 1 and 2 piles were light brown and had a small amount
of agglomerated while the compost materials were dark brown,
loose, homogeneous and without caking in the group 3 and 4
piles. In summary, the group 4 effect was obvious. The finished
composting of group 4 had dark brown color, no odor, obvious
humus flavor and loose structure.

Changes and analysis of temperature and pH during
composting: The change of temperature was an important
indicator for microbial activity, which could reflect the maturity
degree of compost and directly affect the rate of drying [28].
In the initial stage of composting, the content of organic
substances was rich, which were decomposed by the aerobic
microorganism quickly and released heat to increase the piles’
temperature. The optimum composting temperature was 50~60
℃, which was beneficial to kill pathogens in the soil. Too
high or too low temperature was not beneficial to the process
of cow manure composting. Too low temperature affected
the decomposition rate of organic matter. On the contrary, it
could inhibit and even kill some normal microorganisms [29]. Therefore, the temperature was necessary to kill pathogens,
ensure the qualified hygienic indexes and maturity on aerobic
compost.

In view of Figure 1a, the temperature of group 1, 3 and 4 piles
heated obviously, which was higher than that of group 2. It
was in the second day that group 1, 3 and 4 piles reached high
temperature stage while group 2 pile needed four days, which
indicated the temperature change was mainly influenced by CaO
when CaO and CaO2 were existence in piles. The temperature
of group 4 piles rose to 65 ℃ only needed four days, which
was because of the CaO addition and continuous addition of
CaO2 that made oxygen supplement constantly and promoted
microbial metabolic activity so that the temperature reached
the highest. Therefore, CaO2 as oxygen supplement had a good
effect on rapid drying and deodorization during composting,
especially it worked better together with CaO.

The pH value was also an important parameter of aerobic
microbial activity in composting process. It was researched
that the best pH value of microorganisms was neutral or weak
alkaline. When pH value was below 4.5 or more than 10.5,
it would seriously affect microbial activity that most of the
bacterial activity was weakened [30]. The change of pH value
during composting was the result of the interaction of organic
acids produced by carbon organic compounds, ammonia and
proteins [31,32].

Figure 1b showed the pH trend on compost with time. In the
initial stage of composting, the detection value of pH fluctuates greatly because of the addition of CaO and CaO2. Among them,
the pH value of group 2 pile was lower than other three groups,
which may be as a result of the CaO without expansion. Then
the pH value of four groups tended to stabilize and remained
between 8~9 with the compost time going on. At the end of
composting, the pH value of each group was kept below 9,
which was suitable for the optimum environment for microbial
growth of compost.

Figure 1: Temperature and pH changes of composting piles;(a)Change of temperature in different groups, (b)Change of pH in different groups.

Variation and analysis of moisture and organic matters:
Moisture was also a very important parameter of composting
as microbial material took only water-soluble nutrients. It was
directly affecting the processing speed and maturity of cattle
manure [33,34]. The moisture content, too high or too low would
have a negative impact on the aerobic microbial decomposition
and metabolic activities [35]. It was generally believed that the
optimum moisture of compost was about 50%~60% [36,37].
Adding CaO and CaO2 to groups of 3 and 4 piles, the water
content of composting was lower than that of group 1 and 2,
because the reaction among CaO, CaO2 and water, released
heat and oxygen and promoted the evaporation of water during
composting.

It was showed that moisture changes of piles had the same trend
in 30 days composting (Figure 2a). There had obvious change of
group 1, 3 and 4 piles moisture, which were kept below group 2
pile after 30 days composting. Although moisture of each group
dropped to below 30% at the end of composting, the moisture of
group 3 and 4 piles were the lowest, both of which were 23.5%.
It was far lower than group 1 and 2 pile at 25.1% and 27.8%
respectively, which indicated that CaO and CaO2 had certain synergy effects on the decline of composting piles moisture no
matter what the way to adding. What’s more, fluctuations of
moisture might be impacted by rainfall.

The organic compounds were gradually oxidized and
decomposed by aerobic microorganisms in the process of
composting [38,39]. At the same time, the contents of TN, TP
and TK remained relatively stable or slightly increased and the
fertilizer efficiency could be continuously enhanced [40-44].
The organics were decomposed into CO2, water and minerals
in the process of composting. The decomposition products were
also synthesized into new hemic substances under the action of
microorganisms. According to Figure 2b, the organic matters
in all experiment group piles had a certain reduction. However,
the organics of group 4 decreased the most, which was mostly
because the continuous addition of CaO2 that could provide
more oxygen to the compost in the piles in the high temperature
stage. What’s more, the microorganisms’ metabolic activities
could consume more organic matter in the composting piles
with the addition of CaO2.

Figure 2: Variation of moisture and organic matters in different group piles;(a)Changes of moisture in different groups,(b)Changes of organic matter in different groups.

Change of total nitrogen, phosphorus and potassium content: Due to the organic matter decomposition by microorganisms
during composting, however, generally the TN concentration
slightly decreased or the TP and TK concentration increased
slightly during composting due to the concentration effect. The
changes of each group of TN contents in the composting process
showed first decrease and then increase (Figure 3a). At the end
of the compost, the TN content of each treatment group was
less than the initial TN content. The final TN content of group
2 pile was greater than that of the other groups. However, the
initial TN content of group 2 pile value was much larger than
the other groups. Furthermore, the TN content of group 2 piles
reduced the largest. Therefore, about TN loss in group 2 piles
greatly needed to be further research and analyzed during the
composting process.

The TP in four group piles showed a trend for “rising and
falling” in the process of composting (Figure 3b). At the end
of composting, the TP of group 1 and 3 piles was larger than
the initial value. However, the TP of group 1 pile was greater
than other groups at final while the initial TP content of group
1 pile was smaller than in the other three groups. Furthermore,
the TP content of group 1 was increased the largest. Therefore,
about TP increased greatly on group 1 pile needed to be further
research and analyzed during the composting process.

It was shown that the changes of TK in four groups appeared a more regular “down-up-down-up” trend in the composting
process (Figure 3b). At the end of composting, the TK of group
2 and 4 piles was greater than the initial value. However, the
TK of group 2 pile was higher than other three groups at final
while the initial TK content of group 2 was smaller than other
groups. Furthermore, the TK content of group 2 was increased
the largest. Therefore, about TK increased greatly on group 2
pile also needed to be further research and analyzed during the
composting.

Figure 3: Change of TN, TP and TK content in different groups;(a)Change of TN in different groups,(b)Change of TP and TK in different groups.

Changes and analysis of biomass properties of compost
materials

OTU rarefaction: The OTU rarefaction curve could be used to
compare the richness of different sample species with different
sequencing numbers and it was also to indicate whether the
sampling was reasonable. When the curve flattened out, it was
indicated that the sampling depth had been basically covered
in all the species in the sample [45,46]. In Figure 4, except in
the start-up and initial heating period, OTU rarefaction curve
were almost leveled off, which indicated that sampling had been
basically covered in all the species.

Figure 4: OTU rarefaction curve in sample.(Horizontal axis: the number of sequences randomly selected from the sample; Vertical axis: the number of OTU constructed based on the number of sequenced number. 1.1 as the group 1; 1.2 as the group 2; 1.3 as the group 3; 1.4 as the group 4; A represents the start-up phase samples, B, C, D on behalf of the heating period samples, E, F, G on behalf of the high temperature samples, H on behalf of the maturity of samples, I represents microbial agent).

In Figure 4, it was shown that the OTU rarefaction curve in
four experiment group piles were shaking in the start-up and
initial warming period, because the microbial bacteria began
to multiply during aerobic composting. Therefore, the richness
of four experiment group piles were relative larger especially
group 2 pile. During the high temperature period, the OTU
rarefaction curve of group 1, 2 and 3 sample were leveled off
while the OTU rarefaction curve of group 4 sample was always
shaking, because the composting pile need to be turned when the
continue addition of CaO2 happens. In the maturity period, the
OTU rarefaction curve of four experiment groups were almost
leveled off, which might be the species of microbial bacteria
tend to be stable. What’s more, the OTU rarefaction curve of the
effective microbial agent was also displayed in the bottom of Figure 4. The results showed that the sampling on the ordinary
effective microbial agent was also basically covered in all the
species and its richness was worse than four experiment group
piles at any time.

Alpha diversity: Alpha diversity is the biological diversity
within the sample, which is not related to other samples. The
Alpha diversity of microorganism in each sample having the
parameters of calculation are included PD_whole_tree, Chao1,
Shannon as well as Simpson and so on [47,48]. The Chao1 and
the PD_whole_tree indexes reflect the richness of community in the sample, which simply refers to the number of species
(number of OTU), or to the abundance of each species in the
community. The greater the value, the more abundant species
were in samples.

In Figures 5a and 5b, it was shown that the charts of PD_whole_
tree and the Chao1 indexes in four experiment group piles were
shaking and the index value was greater in the start-up and
initial warming period, because the microbial bacteria began to
multiply during aerobic composting. So, the sampling was hard
to include all the number of microbial. The differences between
in start-up as well as initial warming period and warming, high
temperature as well as maturity period in the chart of Chao1
index was obvious than that in PD_whole_tree. During the
high temperature period, the index value of PD_whole_tree
and Chao1 curve of group 1, 2 and 3 piles were almost leveled
off and the values were basically in the same while the group
4 pile was shaking and the value was higher than other there
groups, because the composting pile need to be turned with
the continue addition of CaO2. In the maturity period, the PD_
whole_tree and Chao1 curve of four experiment group piles
were leveled off, and the species of microbial bacteria tend to
be stable. What’s more, the PD_whole_tree and Chao1 curve of
the effective microbial agent was also displayed in the bottom
of Figure 5a and b. The results showed that the richness on the
ordinary effective microbial agent was worse than experiment
compost in each period.

Shannon and Simpson reflect the index of microbial diversity in
the sample. In Figure 5c, the Shannon curve rose in a straight
line at first, because the number of the sequence was not enough to cover the samples. With the composting going, the curve
flattened out, which indicated that the sequencing data was
large enough to reflect the vast majority of microbial species
information in the sample. This was consistent with the results
of OTU rarefaction curve.

The Simpson curve was used to estimate the diversity of
microorganisms in the samples and it was proposed by Edward
Hugh Simpson (1949). It was used to quantitatively describe
the biodiversity of a region in ecology. The larger the Simpson
index, the higher the diversity of community [49,50]. In Figure
5d, it was showed that the Simpson curve in four experiment
group piles were larger in the start-up, especially group 2 pile,
because the addition of CaO2 make the microbial bacteria began
to multiply. During the warming and high temperature period,
the Simpson value would slightly reduce, which might because
the microbes was screened by composting temperature. In the
maturity period, the Simpson index of group 3 pile was slightly
higher than other there groups, because the addition of CaO and
CaO2 made the suitable moisture, temperature and more oxygen.
What’s more, the Simpson curve of the effective microbial
agent was also displayed in the bottom of Figure 5d. The results
showed that the diversity on microbial of piles’ sampling was
larger than the ordinary effective microbial agent.

Figure 5: The PD_whole_tree, Chao1, Shannon and Simpson curve in sample.(1.1 as the group 1; 1.2 as the group 2; 1.3 as the group 3; 1.4 as the group 4; A represents the start-up phase samples, B, C, D on behalf of the heating period samples, E, F, G on behalf of the high temperature samples, H on behalf of the maturity of samples, I represents microbial agent).

Relative abundance was used to explain two aspects of sample
diversity, which were the richness and uniformity of the species
in the sample. The richness of the species was reflected by the
length of the curve on the horizontal axis. The wider the curve,
the richer the composition was in the species. The uniform
degree of species composition was reflected by the shape of the curve, the flatter the curve, the higher the uniformity were the
species [51].

In Figure 6, it was shown that the relative abundance curve
in four experiment group piles were wider and uniform in the
start-up period, because indigenous microorganism began to
multiply. During the warming and high temperature period,
the relative abundance curve became slightly narrow, which
might be the microbes screened by composting temperature. In
the maturity period, the four group piles had little difference.
What’s more, the relative abundance curve of the effective
microbial agent was also displayed. The curve was both short
and narrow compared with the four experiment group, which
indicated that the species richness and uniformity of ordinary
effective microbial agent was worse than four experiment group
piles.

Figure 6: Relative abundance in sample.(1.1 as the group 1; 1.2 as the group 2; 1.3 as the group 3; 1.4 as the group 4; A represents the start-up phase samples, B, C, D on behalf of the heating period samples, E, F, G on behalf of the high temperature samples, H on behalf of the maturity of samples, I represents microbial agent).

Beta diversity: Beta diversity is the comparison of biological
diversity among samples, which has no related to other
samples. Commonly the Unifrac methods and Nonmetric
Multidimensional Scaling (NMDS) were used to calculate
Unweight or Weighted matrices. Then, according to this matrix,
the analysis of PCoA and NMDS were carried out. The difference
between individuals or groups can be observed through PCoA.
The closer distance between two samples on the axis, the more
similar to two samples were [52,53]

As shown in Figure 7 (a), the PCoA diagram of the sample was
analyzed under Unweight. In initial stage of composting, the
microbial composition of 2, 3 and 4 group samples had little
difference. Group 1 sample had large difference with other three
groups, which might because there was not enough oxygen supply without CaO2. In the heating period of composting,
the microbial composition of four experiment group samples
had little difference. With the composting going, the four
groups began to have some difference. However, the microbial
composition between group 3 and 4 samples was more similar
because of the shorter distance in the PCoA diagram. In the
whole high temperature period of compost, the distance among
in group 2, 3 and 4 group samples were closer, which might be
related to the similar oxygen content. At the end of composting,
the distance among four experiment group samples were close.
Combined with the above physical and biomass properties
analysis, it was had the strengthening effect on rapid biological
drying of dairy cattle manure with the addition of CaO, CaO2 as
well as CaO and CaO2 of which the CaO and CaO2 had some
synergistic effects.

As shown in Figure 7 (b), the PCoA diagram of the sample was
analyzed under Weighted. Similar to those under Unweight
in the initial stage and the heating period of composting, the
microbial composition of group 2, 3 and 4 samples had little
difference in initial stage of composting. Group 1 sample also
had large difference with other three groups. The microbial
composition of four experiment group samples had little
difference in the heating period of composting. However, there
had some differences with analysis under Unweight in the whole
high temperature period of compost. With the composting, the
distance between in group 2 and group 4 samples were closer,
which might be related to the similar content of CaO2. At the
end of composting, the distance among four experiment group
piles were close. Combined with analysis on Unweighted, it was had the strengthening effect on rapid biological drying of dairy
cattle manure with the addition of CaO, CaO2 as well as CaO
and CaO2.

NMDS is characterized by the information contained in the
sample, which is reflected in the multi-dimensional space in
the form of points. The degree of difference between different
samples is shown by the distance among points and finally the
spatial location map of the sample is obtained.

As shown in Figure 7 (c), the NMDS diagram of the sample
was analyzed under Unweighted. In initial stage of composting,
the microbial composition of group 2, 3 and 4 samples had
some difference. Group 1 sample also had large difference with
other three groups, which also might be related to CaO2. In the
heating period of composting, the microbial composition of four
experiment group samples also had a little difference. With the
composting going, the four groups began to have some obvious
differences. However, the microbial composition between
group 1 and group 4 samples as well as group 1 sample and
group 4 sample was more similar because of the shorter distance
in the NMDS diagram. In the whole high temperature period
of compost, the distance among in group 2, 3 and 4 samples
were closer, which also might be related to the similar content
of oxygen. At the end of composting, the distance among four
experiment group samples were also close. The analysis results
were consistent with the PCoA analysis of the sample under
Unweighted.

As shown in Figure 7 (d), the NMDS diagram of the sample
was analyzed under Weighted. Similar to those analyze under
Unweighted in the initial stage and the heating period of composting, the microbial composition of group 2, 3 and
4 samples had little difference. Group 1 sample had large
difference with other three groups. In the heating period of
composting, the microbial composition of four experiment
group samples also had a little difference. The distance between
in group 1 and group 2 samples as well as between group 3
and group 4 samples was relative closer respectively. However,
there had some differences with analysis on piles under
Unweighted in the whole high temperature period of compost.
With the composting, the distance between in group1 and group
4 samples were closer, which also might be related to the similar
content CaO. At the end of composting, the distance among
four experiment group samples were close. The analysis results
were consistent with the PCoA analysis on the sample under
Weighted.

Figure 7: Chart of PCoA and NMDS (Unweight and Weighted Unifrac);(a) Chart of PCoA under Unweighted Unifrac, (b) Chart of PCoA under Weighted Unifrac, (c) Chart of NMDS under Unweighted Unifrac, (d) Chart of NMDS under Weighted Unifrac. (1.1 as the group 1; 1.2 as the group 2; 1.3 as the group 3; 1.4 as the group 4; A represents the start-up phase samples, B, C, D on behalf of the heating period samples, E, F, G on behalf of the high temperature samples, H on behalf of the maturity of samples, I represents microbial agent).

Conclusion and Prospect

All physical indexes detected in the experiments were accorded
with the national standard of organic fertilizer agriculture. The
CaO and CaO2 could accelerate the temperature rise, advance
the reactor piles into high temperature stages and reduce water
content of the composting piles rapidly. At the end of compost, the
moisture decreased to below 30% and decreased by 6.0%~8.0%
compared with the control group 1 and 2 piles. What’s more, no
matter alpha or beta diversity in four experiment group piles had
little difference at the end of the compost. They only had some
changes in the process of compost.

Combined with the physical and biomass properties analysis,
it was had the strengthening effect on rapid biological drying
of dairy cattle manure with the addition of CaO, CaO2 as well as CaO and CaO2, of which the CaO and CaO2 (cont.) had the
best effects on cow manure composting in the research. It was
in the second days that composting came into high temperature
stage. In the heating stage, it was only in fourth days that the
temperature reached the highest 65℃ and the heating effect was
remarkable. At the end of the composting, the moisture was
23.5%. Compared with other treatment groups, the moisture
content decreased to minimum value, which was far better than
the specified value of agricultural organic fertilizer standard
(30%). What’s more, the pH values of all cow manure piles
were only about 9.0 after composting rotten, which could be well neutralized by the gradually acidified soil in the southwest
of China.

The following researches we will study and analyze further
about TN loss in group 2, TP increased greatly on group 1 and
TK increased greatly on group 2 during the composting.

Acknowledgement

The work was financially supported by the National Major
Science and Technology Project [Grant NO. 2014ZX07105-
001]; the National Natural Science Foundation of China [No.
21377048].

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